This proposal explores the role of the central biogenic amines in learned behavior. The particular behavior selected for study is the conditioned taste aversion. This behavior is usually defined as the avoidance of a taste cue which has previously been paired with an event which is presumed to cause some form of illness. Exposure to radiation or administration of any of a variety of drugs can be used to induce an aversion. Recent data suggest that the manipulation of levels of endogenous amines can be used to block or facilitate taste aversion learning. Depletion of central catecholamines impairs the formation of aversions to saccharin solution if amphetamine is used to induce the aversion. On the other hand, depletion of serotonin has been shown to enhance lithium chloride-induced aversions. Furthermore, the association of taste and lithium-induced toxicosis can be impaired if the immediate precursor of serotonin is administered prior to conditioning and serotonin levels are elevated. The objective of this proposal is to explore the generality of these findings and to determine the nature of the role of the biogenic amines in taste aversion learning. Chemical neurotoxins will be used to selectively deplete norepinephrine, dopamine or serotonin in specific brain areas. The effects of chemically specific lesions on aversions produced by different types of drugs will be established. Drugs thought to exert their effects peripherally to induce taste aversions will be compared to psychotropic drugs thought to produce aversions by a direct action on the central nervous system. Depletion of amines will be monitored with fluorometric assay techniques. Furthermore, attempts will be made to determine whether the reported effects of non-specific electrolytic brain lesions on taste aversion learning may in some cases have been due to damage to amine systems. Finally, the effects of elevating amine levels on conditioned taste aversions will also be explored.